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Overheating but appears very rich

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apollo1983

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Hi,

I'm trying to tune a Picco .26 in my Jammin X1 buggy, but am having some issues. I'm new to Nitro and this buggy -- I've read a lot on the forum and learned quite a bit, but wanted to ask a question.

Currently I feel like the needle settings are pretty decent, all indicators seem to lean towards it being rich. There's plenty of blue smoke, a little bit of unburnt fuel coming out the exhaust. I've also toyed with the needles so that if I richen them any more, the car will not start.

It runs pretty decent for the first few minutes, but as I continue to do some passes, and check the temp, it just keeps on going, I stop it at 300 out of fear. I am using a Duratrax temp gauge, which I've heard bad things about, but the spit test confirms it's darn hot. I can't richen any more at this point with the needles.

I've tried the easy things, fresh fuel, new plug, new fuel lines. I've also done some preliminary checking of the motor for air leaks but haven't found anything so far. I"m going to take it out of the car tonight and really test it.

So, all I've read seems to indicate some sort of air leak. The question I have, is if it's an air leak, why is the blue smoke and unburnt fuel still coming out the exhaust? I would think if it leaned out due to an air leak, these "rich indicators" would stop.

Is that not the case? If not, does the fact these indicators are still there point to/rule out a certain part of the system being the cause?

Thanks!
 
It's sounds like your HSN is a bit too lean. Try to richen up the HSN and lean out the LSN just a bit.
 
Put sealant on the carb where the aluminum end cap joins with the composite body of the carb. Older Picco's are known for sucking air at this area, but only when the engine is hot. Also follow the above advice. Acceleration comes from the LSN. Use a long medium cool plug and 30% fuel with low oil content such as Byron's 30% race blend or pro blend. I recommend the O'Donnell's purple sport plugs. Cheap and very durable.
Just thought about another Picco specific problem, the round smooth exhaust port. Regular 1/8th scale header gaskets do not seal properly on Picco's. I use the purple HPI gaskets for the Savage. They seal nicely.
 
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Ok - thanks for the advice! Tonight I took out the engine and gas tank to check for leaks. I found a small tear in the rubber boot that covers the throttle. I hope it was not a self created issue caused by me blowing too hard into the thing while checking the backplate, but in any case it's an issue now. Is this possible to repair with hi-temp gasket stuff, or is this something I have to replace?

Right now I'm using Byron's 20%, and an Odonell #99. The logic was less nitro, more lube, mo safe, it was a LHS recommendation. I will look into using the HPI gasket, I did notice the header gasket was a bit chincy when I took it off.
 
boot not an issue

found a old boot in a spare parts bin and fitted it, so that should no longer be an issue... so it should be all sealed now, back to tuning and I'll see how it goes.
 
Let us know how it works out. More oil does offer more protection, but higher nitro and less oil burns much cooler and makes the tuning process a lot easier. You are actually running richer needle settings with 30% vs 20% so there really is very little difference in the amount of lubrication.
Between the carb boot and the exhaust gasket I'd say you solved your issue. The carb boots will not develop a hole from air pressure, they dry rot or get punctured. Usually throttle return springs and header springs are the culprit.
 
I still have the same results, this is darn frustrating. I tried various settings, leaning out the LSN and richening the HSN. If I go any leaner on the LSN it won't run, and and richer on the HSN it won't run....so I feel like I've hit a wall. Any setting I can get the engine to stay running with overheats it.

I'm pretty sure I don't have any leaks since I took everything out on Friday and tested it... but there has to be...right?

Could 20% be causing this? You said 30% is supposed to run cooler, but I wouldn't think there is a 75-100 degree difference. I know the previous owner ran 30%...should I try that?
 

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